Endocrine Disorders


Addison's Disease (Hypoadrenocorticism)

Addison’s disease is a disorder resulting from insufficient adrenal hormone (glucocorticoid and/or mineralocorticoid) secretion. Insufficient adrenal hormones can disrupt the body’s regulation of sodium and potassium, reduce circulating blood volume, impair heart and kidney function and impair sugar and fat metabolism. The syndrome is uncommon in dogs but well recognized; it is rare in cats. Causes include neoplasia, immune disorders, fungal granulomas, drugs (eg. mitotane) and hemorrhage. Signs may mimic many other disorders but include weakness, depression, collapse and death. Diagnosis is afforded by physical exam, complete blood count, blood chemistries, urinalysis, electrocardiography, abdominal x-rays and ACTH stimulation test. (ACTH, adrenocorticotrophic hormone). Treatment may include hospitalization with intravenous fluid and electrolyte supplementation, mineralocorticoid (eg. flurocortisone, desoxycorticosterone) and glucocorticoid (eg. prednisolone, prednisone) therapy.

Cushing's Disease (Hyperadrenocorticism)

Cushing’s disease is a syndrome resulting from excessive adrenal hormone (glucocorticoid). Causes of Cushing’s disease are excessive secretion of ACTH (adrenocorticotrophic hormone) from the pituitary gland, adrenocortical tumor and excessive or prolonged administration of glucocorticoid medications. Signs of the disorder may include distended (“pot-bellied”) abdomen, symmetrical hair loss, thin skin, hyperpigmented (darkened) skin, mineralization of skin patches, muscle atrophy, increased thirsty, increased urination, increased appetite, diarrhea, listlessness, excessive panting, lethargy, circling, seizure and decreased fertility. Diagnosis is afforded via physical exam, complete blood count, blood chemistries, ultrasonagraphy, abdominal x-rays, ACTH stimulation test, dexamethasone suppression tests and urinary cortisol:creatinine ratio. Treatment may include medication (eg. selegiline, mitotane, ketoconazole) and/or surgery.
Cushing’s syndrome or hyperadrenocorticism is a disorder characterized by excessive production of cortisol by the adrenal gland. The adrenal glands (small bean-shaped glands located near the kidneys) most often produce excess cortisol due to chronic stimulation by the master hormone gland, the pituitary (a pea-shaped gland at the base of the brain). However, 10-15% of dogs with Cushing’s syndrome have high cortisol levels due to an adrenal tumor secreting cortisol. Some pets may acquire iatrogenic (caused by therapy) Cushing’s as a result of long term, high dosage glucocorticoid therapy. Signs of hyperadrenocorticism include poor hair coat and hair loss, weakness, enlarged belly, increased thirst and urination, and increased appetite. Dogs with Cushing’s syndrome are also prone to infections and diabetes mellitus. Various blood tests and ultrasound performed by your veterinarian help to distinguish the cause of the Cushing’s syndrome. Treatment is aimed at decreasing the cortisol levels. In dogs with an adrenal gland tumor, surgery is recommended to remove the tumor. However, in dogs with overly active adrenal glands secondary to pituitary stimulation, treatment with medication (eg. o,p DDD and selegiline) decreases cortisol secretion. Your veterinarian must adjust the dose of this medication to the particular needs of your pet. Surgery may be curative if the adrenal tumor is benign while medical treatment is only a control of Cushing’s syndrome. Patients periodically come out of remission and need to be re-evaluated by your veterinarian. Many patients improve dramatically with regrowth of hair, decrease in thirst, urination, appetite, and return to general good health.

Diabetes Insipidus

Coughs are produced by irritation of the windpipe (trachea) and/or lung. Inflammation, foreign bodies, infections (eg. kennel cough) and heart disease may contribute to a cough. Treatment is directed at the etiology of the cough. Anti-inflammatories, antibiotics, heart medication and surgery/endoscopy may be used to treat a cough. Prevention or minimization of the cough can be afforded via vaccination against respiratory disease (eg. kennel cough), early treatment of heart disease and the avoidance of dangerous toys/items that may be aspirated or dusty/allergen laden areas.

Diabetes Mellitus

Diabetes mellitus is a disorder caused by a deficiency of insulin or a lack of proper response to insulin. Insulin is a hormone produced by cells within the pancreas and is necessary for the body to utilize sugar. Lack of insulin or its effects, results in sugar remaining in the blood and then being passed in the urine. Signs of the disorder includes increased urination, increased thirst, increased hunger, weight loss, cataracts and standing on hocks (cats). Further signs of uncontrolled diabetes mellitus include vomiting, diarrhea, skin infections, bladder infections, depression, slow/deep breathing, collapse and death. Diagnosis is afforded via physical exam, complete blood count, blood chemistries and urinalysis. Treatment is directed at controlling blood sugar and the secondary complications of high and possibly low blood sugar. Insulin therapy is the mainstay of controlling diabetes mellitus. Oral hypoglycemic drugs can be utilized with some non insulin dependent diabetic cats. Special diets are also an integral part of treatment.


Hyperthyroidism is a disease characterized by excessive production of thyroid hormones by the thyroid glands. The thyroid glands (small glands located along side the voicebox and windpipe) frequently develop tumors in old cats, resulting in excess production of thyroid hormone. Causes include hyperplasia (non-cancerous growth) or neoplasia (only 1-2% of all cases). The reason these glands develop hyperplasia or tumors is not known but is seen more often in older cats. High levels of thyroid hormone may affect your pet’s health in several ways. Signs of excessive thyroid production include weight loss despite a ravenous appetite, vomiting, diarrhea, frequent bowel movements, increased thirst and urination, restlessness, frequent crying or vocalizing, neglect of normal grooming, lethargy, muscle weakness, trouble breathing (dyspnea) and rapid heart beat. The effects on the heart may be severe and result in congestive heart failure. Diagnosis is afforded via physical exam, complete blood count, blood chemistries, laboratory tests (including free T4) and special imaging studies. Treatment may include medication (eg. methimazole), surgical removal of the glands and/or radioactive iodine therapy (to destroy all thyroid tissue). Many cats must be prepared for surgery by administration of medications designed to decrease thyroid hormones levels and to decrease the effects of hyperthyroidism prior to surgery. In the presence of heart disease medical treatment is used until the pet is healthy enough to undergo surgery or radioactive therapy. If either such drug therapy is appropriate for your cat, periodic reassessment of thyroid hormone levels, physical examinations and heart evaluations may be necessary before surgery is recommended. In some cases, a nuclear scan of the thyroid gland is needed to ensure correct identification of the location of the thyroid tumor before surgical removal is attempted. Following surgery, the most serious problem is low blood calcium due to inadvertent removal of the parathyroid glands. This problem rarely occurs with experienced surgeons.


Hypothyroidism is a disease caused by thyroid hormone deficiency. The pituitary gland may be involved (decreased thyroid stimulating hormone), but most cases are due to inadequate production of hormones by the thyroid glands. The disease occurs most frequently in middle-aged dogs, particularly mid- to large-sized breeds. Causes include degenerative disorders, congenital (present at birth) or juvenile-onset disease, neoplasia, immune disorders, trauma (eg. surgical removal of glands) and toxins (radioactive therapy). Signs may include exercise intolerance, increased sleeping, reduced tolerance to cold, dry coat and skin, premature graying of the muzzle, hair loss, slow hair growth, recurrent skin infections , thickened skin, dark skin pigment, neurologic disorders and a slow heart beat. Females may have irregular cycles and/or reduced fertility. Males may have a shrinkage of the testicles and show less interest in females. Diagnosis is afforded via physical exam, complete blood count, blood chemistries, laboratory test (including free T4) and thyroid biopsy. Treatment of choice is thyroid hormone supplementation along with treatment of secondary disorders.

Nutritional Secondary Hyperparathyroidism

Nutritional secondary hyperparathyroidism occurs in animals fed diets containing improper amounts of calcium and phosphorus. It is most common in younger cats (also older birds and reptiles). The disease develops in the following manner:

  • A properly balanced diet for your pet (eg. premium commercial diet) contains nearly equal amounts of calcium and phosphorus. However, most meats and vegetables contain very high levels of phosphorus in relation to calcium. Beef liver and some vegetables may contain 50 times as much phosphorus as calcium. When such foods constitutes the main diet, more phosphorus than calcium enters the animal’s bloodstream.
  • The parathyroid glands (small glands in the neck) produce a hormone that maintains the proper proportions of calcium and phosphorus. Since little dietary calcium is available, the needed calcium must come from the animal’s own bones!
  • Removal of excess calcium from the bones severely weakens them. Lack of proper calcium levels also effects muscle and heart function.

Signs of nutritional secondary hyperparathyroidism may include weakness, pain, bone fractures and death. Diagnosis is afforded via accurate history, physical exam, complete blood count, blood chemistries and radiography (x-rays). Treatment includes a proper balanced diet and parental (eg. intravenous) nutritional support until the patient is stable and eating on its own.